Pulsed terahertz quantum-cascade laser has peak power of 1.01 W

Leeds, England--A 3.4-THz-emitting quantum-cascade laser (QCL) created by a group at the School of Electronic and Electrical Engineering, University of Leeds, reaches a pulsed peak power of up to 1.01 W from a single facet when cooled to 10 K.¹ The laser output is achieved using a broad-area configuration.

An aluminum gallium arsenide- based (Al_0.16Ga_0.84As/GaAs) heterostructure was grown on a semi-insulating GaAs substrate; ridges of widths from 145 to 425 μm were pholithographically created. In the experiment, the lasers were pulsed at 10 kHz and a 2% duty cycle and cooled by liquid helium.

A version with a 3-mm-long cavity and a 425-μm-wide ridge emitted a peak power of 780 mW; when one facet was coated with a high-reflectivity coating, the peak power was boosted to 1.01 W.

This output more than doubles the output levels in terahertz QCLs developed ar the Massachusetts Institute of Technology (MIT; Cambridge, MA) and subsequently by a team from the Vienna University of Technology (Vienna, Austria) last year.

Widely publicized potential applications of terahertz radiation include monitoring pharmaceutical products, remote sensing of chemical signatures of explosives in unopened envelopes, and noninvasive detection of cancers in the human body. “Although it is possible to build large instruments that generate powerful beams of terahertz radiation, these instruments are only useful for a limited set of applications," says Edmund Linfield, one of the University of Leeds researchers. "We need terahertz lasers that not only offer high power but are also portable and low cost."

The quantum cascade terahertz lasers being developed by Leeds are only a few square millimeters in size.

The work was mainly funded by the Engineering and Physical Sciences Research Council (EPSRC; Swindon, England).

REFERENCE:

1. Lianhe Li et al., Electronics Letters (2014); doi: 10.1049/el.2013.4035